U.S. patent number 4,406,673 [Application Number 06/217,582] was granted by the patent office on 1983-09-27 for ultrathin solid membrane, process for production thereof, and use thereof for concentrating a specified gas in a gaseous mixture.
This patent grant is currently assigned to Teijin Limited. Invention is credited to Shizuo Azuma, Shizuka Kurisu, Kiyoshi Sugie, Takeyoshi Yamada, Teizo Yamaji.
United States Patent |
4,406,673 |
Yamada , et al. |
September 27, 1983 |
**Please see images for:
( Certificate of Correction ) ** |
Ultrathin solid membrane, process for production thereof, and use
thereof for concentrating a specified gas in a gaseous mixture
Abstract
A process for producing ultrathin solid membranes from a solvent
solution of an addition polymer derived from an ethylenically
unsaturated hydrocarbon monomer or a conjugated unsaturated
hydrocarbon monomer in a solvent composed mainly of a volatile,
substantially water-immiscible organic liquid medium capable of
dissolving the addition polymer and another organic compound having
a distribution coefficient k, which is the ratio of the
concentration of the other organic compound in the organic liquid
medium to that in water, of from 0.5 to 35. The solvent satisfies
the equation wherein c.sub.1 is the surface tension (dynes/cm) of
water, a.sub.1 is the surface tension (dynes/cm) of the solution of
the addition polymer in the solvent, and b.sub.1 is the interfacial
tension (dynes/cm) between the solvent solution and water. The
solvent solution of the addition polymer is allowed to spread
spontaneously on the surface of a liquid support consisting
substantially of water whereby the solvent in the solvent solution
is removed to an amount sufficient to form a solid membrane on the
surface of the liquid support. The process may be performed
batchwise or continuously. The solid membrane can be used for
obtaining a gas having a specified component gas concentrated
therein, for example, a gaseous mixture having enriched oxygen gas
from a gaseous mixture of two or more gases for example air.
Inventors: |
Yamada; Takeyoshi (Iwakuni,
JP), Kurisu; Shizuka (Iwakuni, JP), Azuma;
Shizuo (Iwakuni, JP), Sugie; Kiyoshi (Iwakuni,
JP), Yamaji; Teizo (Iwakuni, JP) |
Assignee: |
Teijin Limited (Osaka,
JP)
|
Family
ID: |
27524400 |
Appl.
No.: |
06/217,582 |
Filed: |
December 18, 1980 |
Foreign Application Priority Data
|
|
|
|
|
Dec 27, 1979 [JP] |
|
|
54-169461 |
Jun 2, 1980 [JP] |
|
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55-72678 |
Jul 14, 1980 [JP] |
|
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55-95057 |
Nov 6, 1980 [JP] |
|
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55-155197 |
Nov 6, 1980 [JP] |
|
|
55-155198 |
|
Current U.S.
Class: |
95/54; 264/45.1;
96/12 |
Current CPC
Class: |
B01D
53/22 (20130101); B01D 69/122 (20130101); B29D
7/01 (20130101); B01D 71/26 (20130101); B01D
2313/38 (20130101) |
Current International
Class: |
B01D
53/22 (20060101); B01D 69/00 (20060101); B01D
71/26 (20060101); B01D 69/12 (20060101); B01D
71/00 (20060101); B29D 7/01 (20060101); B29D
7/00 (20060101); B01D 053/22 (); B01D 039/16 () |
Field of
Search: |
;264/298,41,45.1
;55/16,158 ;210/640,500.2 ;525/42,106 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Spear, Jr.; Frank A.
Attorney, Agent or Firm: Sherman & Shalloway
Claims
What we claim is:
1. A process for producing an ultrathin solid membrane, which
comprises dissolving an addition polymer derived from at least one
monomer having from 2 to 20 carbon atoms and selected from the
group consisting of ethylenically unsaturated hydrocarbon monomers
and conjugated unsaturated hydrocarbon monomers in a solvent
composed mainly of volatile, substantially water-immiscible organic
liquid medium capable of dissolving the addition polymer and being
selected from the group consisting of a hydrocarbon and a
halogenated hydrocarbon, said solvent containing 0.1 to 15% by
weight of another organic compound selected from the group
consisting of alicyclic alcohols, aromatic alcohols, ketones,
aldehydes, carboxylic acids, peroxides, and mixtures thereof, said
organic compound having a distribution coefficient k, which is the
ratio of the concentration of the other organic compound in the
organic liquid medium to that in water, of from 0.5 to 35, and said
solvent meeting the following equation
wherein c.sub.1 is the surface tension (dynes/cm) of water, a.sub.1
is the surface tension (dynes/cm) of the solution of the addition
polymer in the solvent, and b.sub.1 is the interfacial tension
(dynes/cm) between the solvent solution and water, and thereafter
allowing the solvent solution of the addition polymer to spread
spontaneously on the surface of a liquid support consisting
substantially of water whereby the solvent in the solvent solution
is removed to an amount sufficient to form a solid membrane on the
surface of the liquid support.
2. The process of claim 1 wherein the solvent meets the following
equation
wherein a.sub.1, b.sub.1, and c.sub.1 are as defined in claim
1.
3. The process of claim 1 wherein the other organic compound has a
distribution coefficient k of 1.0 to 25.
4. The process of claim 1 wherein the hydrocarbon or halogenated
hydrocarbon is an alicyclic or aromatic compound.
5. The process of claim 1 wherein the organic liquid medium is
selected from the group consisting of cyclohexene, cyclohexane,
trichloroethylene, trichloroethane, tetrachloroethane,
trichloropropane and the mixtures thereof.
6. The process of claim 1 wherein the other organic compound is
selected from the group consisting of cyclohexenol, cyclohexanol,
phenol, cyclohexenone, cyclohexylamine, aniline, furfural, benzoic
acid, cyclohexenyl hydroxyperoxide, and the mixtures thereof.
7. The process of claim 1 wherein said ethylenically unsaturated
hydrocarbon monomer or the conjugated unsaturated hydrocarbon
monomer is an aliphatic or cycloaliphatic compound having 2 to 20
carbon atoms.
8. The process of claim 7 wherein the ethylenically unsaturated
hydrocarbon monomer is ethylene, propylene, butene, isobutene,
pentene, methylpentene, hexene, methylhexene, heptene,
cyclohexylpentene, styrene, .alpha.-methylstyrene or a mixture of
these.
9. The process of claim 7 wherein the conjugated unsaturated
hydrocarbon monomer is butadiene, isoprene, cyclooctadiene or a
mixture of these.
10. The process of claim 1 wherein the addition polymer is
polyethylene, polypropylene, polybutene, polyisobutene,
polypentene, polymethylpentene, polyhexene, polymethylhexene,
polyheptene, polycyclohexylpentene, polystyrene,
poly(.alpha.-methylstyrene), poly(1,4-butadiene),
poly(1,2-butadiene), polyisoprene or polycyclooctadiene.
11. The process of claim 1 wherein the solvent solution contains
about 0.5 to about 15% by weight of the addition polymer based on
the solvent solution.
12. A process for continuously producing an ultrathin solid
membrane, which comprises dissolving an addition polymer derived
from at least one monomer having from 2 to 20 carbon atoms and
selected from the group consisting of ethylenically unsaturated
hydrocarbon monomers and conjugated unsaturated hydrocarbon
monomers in a solvent composed mainly of a volatile, substantially
water-immiscible organic liquid medium which is a hydrocarbon or
halogenated hydrocarbon and which is capable of dissolving the
addition polymer, said solvent containing from 0.1 to 15% by weight
of another organic compound selected from the group consisting of
alicyclic alcohols, aromatic alcohols, ketones, aldehydes,
carboxylic acids, peroxides, and mixtures thereof, said organic
compound having a distribution coefficient k, which is the ratio of
the concentration of the other organic solvent in the organic
liquid medium to that in water, of from 0.5 to 35, and said solvent
meeting the following equation
wherein c.sub.1 is the surface tension (dynes/cm) of water, a.sub.1
is the surface tension (dynes/cm) of the solution of the addition
polymer in the solvent, and b.sub.1 is the interfacial tension
(dynes/cm) between the solvent solution and water, thereafter
continuously feeding the resulting solvent solution to the surface
of a liquid support consisting substantially of water from a feed
means for the solvent solution in such a manner that the solvent
solution does not come apart from the surface of the liquid
support, thereby allowing the solvent solution to spread
spontaneously on the liquid surface and continuously removing the
solvent of the solvent solution to an amount sufficient to form a
solid membrane, and thereafter withdrawing the resulting ultrathin
solid membrane upwardly from the liquid surface while it is carried
on a porous sheet-like material.
13. The process of claim 12 wherein said feed means for the solvent
solution is in contact with the liquid surface, or is up to about 3
mm above the liquid surface.
14. The process of claim 12 wherein the feed means for the solvent
solution is a feed opening which is apart from the liquid surface
to an extent of up to about 2 mm below the liquid surface.
15. The process of claim 12 wherein the feed means for the solvent
solution is an opening having an area of about 0.01 mm.sup.2 to
about 3 mm.sup.2 provided at the end of a hollow tube.
16. The process of claim 12 wherein the solvent solution is
continuously fed from the feed means at a rate of about 0.1 to
about 20 cc/min.
17. The process of claim 12 wherein the liquid support is
flowing.
18. The process of claim 17 wherein the solvent solution spreads
spontaneously on the surface of the moving liquid support.
19. The process of claim 17 wherein before the solid membrane
formed on the liquid surface is carried on the porous sheet-like
material, the solid membrane is forcibly taken up at a
substantially constant rate on the surface of the liquid support in
the flowing direction of the liquid support to form a substantially
stable flow of the solid membrane, and then the solid membrane is
carried on the porous sheet-like material which is moving at a rate
substantially corresponding with the rate of flowing of the solid
membrane.
20. The process of claim 12 wherein the addition polymer is
polyethylene, polypropylene, polybutene, polyisobutene,
polypentene, polymethylpentene, polyhexene, polymethylhexene,
polyheptene, polycyclohexylpentene, polystyrene,
poly(.alpha.-methylstyrene), poly(1,4-butadiene),
poly(1,2-butadiene), polyisoprene or polycyclooctadiene.
21. The process of claim 12 wherein the solvent solution contains
about 0.5 to about 15% by weight of the addition polymer based on
the solvent solution and about 0.1 to about 15% by weight of the
other organic compound.
22. A solvent solution of an addition polymer suitable for forming
an ultrathin solid membrane having a thickness of about 50 to about
3000 A, said solvent solution being prepared by dissolving an
addition polymer derived from at least one monomer having from 2 to
20 carbon atoms and selected from the group consisting of
ethylenically unsaturated hydrocarbon monomers and conjugated
unsaturated hydrocarbon monomers in a solvent composed mainly of a
volatile, substantially water-immiscible organic liquid medium
which is a hydrocarbon or a halogenated hydrocarbon and which is
capable of dissolving the addition polymer, said solvent containing
from 0.1 to 15% by weight of another organic compound selected from
the group consisting of alicyclic alcohols, aromatic alcohols,
ketones, aldehydes, carboxylic acids, peroxides, and mixtures
thereof, said organic compound having a distribution coefficient k,
which is the ratio of the concentration of the other organic
solvent in the organic liquid medium to that in water, of from 0.5
to 35, and said solvent meeting the following equation
wherein c.sub.1 is the surface tension (dynes/cm) of water, a.sub.1
is the surface tension (dynes/cm) of the solution of the addition
polymer in the solvent, and b.sub.1 is the interfacial tension
(dynes/cm) between the solvent solution and water.
23. An ultrathin solid membrane having a thickness of about 50 to
about 3000 A prepared from the solvent solution of claim 22.
24. The solvent solution of claim 22 wherein the addition polymer
is polyethylene, polypropylene, polybutene, polyisobutene,
polypentene, polymethylpentene, polyhexene, polymethylhexene,
polyheptene, polycyclohexylpentene, polystyrene,
poly(.alpha.-methylstyrene), poly(1,4-butadiene),
poly(1,2-butadiene), polyisoprene or polycyclooctadiene.
25. The solvent solution of claim 22 which contains about 0.5 to
about 15% by weight of the addition polymer based on the solvent
solution and about 0.1 to about 15% by weight of the other organic
compound.
26. The solvent solution of claim 25 wherein the organic liquid
medium is selected from the group consisting of cyclohexene,
cyclohexane, trichloroethylene, trichloroethane, tetrachloroethane,
trichloropropane and the mixtures thereof and the other organic
compound is selected from the group consisting of cyclohexenol,
cyclohexanol, phenol, cyclohexenone, cyclohexylamine, aniline,
furfural, benzoic acid, cyclohexenyl hydroxyperoxide and the
mixtures thereof.
27. A solid membrane produced by the process of any one of claims 1
to 18.
28. A process for obtaining a gas having a specified component gas
concentrated therein from a gaseous mixture which comprises
contacting the gaseous mixture with any one of the solid membranes
of claim 27 to selectively separate the specified component gas
from said gaseous mixture.
29. The process of claim 28 which is used for obtaining a gaseous
mixture having enriched oxygen gas from a gaseous mixture
comprising at least oxygen and nitrogen.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an ultrathin solid membrane, a process
for production thereof, and use thereof for concentrating a
specified gas such as oxygen gas in a gaseous mixture such as
air.
2. Field of the Invention
For some years, there has been a marked advance in
membrane-dependent separation techniques in various fields. A
technique for separating a gaseous mixture using a membrane,
however, is a relatively recent technological development. The
technical difficulty of separating a specified gas from a gaseous
mixture lies in the development of a material capable of permitting
permeation of the specified gas with sufficient selectivity and at
a sufficient permeating speed and also in the establishment of a
technique for forming such a material into a very thin membrane
having a uniform thickness and a large area.
Generally, the amount of a gas permeating a homogeneous membrane is
defined by the following equation.
wherein
X represents the permeating velocity [cc(STP)/sec.] of the gas,
P is the permeation coefficient [cc(STP)x.multidot.cm/cm.sup.2
.multidot.cmHg.sec] of the gas,
(P.sub.1 -P.sub.2) is the difference of the partial pressures
(cmHg) of the gas on both surfaces of the membrane,
A represents the area (cm.sup.2) of the membrane, and
l is the thickness (cm) of the membrane.
It is clear therefore that once the material of which the membrane
is made and a gas to be permeated are specified, the amount of
permeation of the gas depends upon the thickness and area of the
membrane. It is desired to make the membrane thickness as small as
possible and the area of the membrane as large as possible.
As a prior attempt to produce a membrane having a small thickness
and a large area, there is known a process for producing an
ultrathin membrane by a batchwise technique, which comprises
dropping a solution of a blend of a methylpentene polymer and an
organopolysiloxane-polycarbonate copolymer in a solvent onto the
surface of water to allow the solution to spread spontaneously on
the surface of water (see U.S. Pat. No. 4,192,842). As described in
the specification of this Patent, the use of the
organopolysiloxane-polycarbonate copolymer makes it possible for
the solution to spread spontaneously on the surface of water. The
specification of this U.S. patent also describes a method involving
the use of a solution of the methylpentene polymer alone in a
solvent. Investigations of the present inventors, however, have
shown that the method using such a solution which does not contain
the organopolysiloxane-polycarbonate copolymer did not lead to the
successful production of an ultrathin membrane having a uniform
thickness and a large area. Thus, although the method disclosed in
the above cited U.S. Pat. No. 4,192,842 involving the use of a
solvent solution of the methylpentene polymer alone is one attempt
at the production of an ultrathin membrane, it is at least not easy
to produce an ultrathin membrane having a uniform thickness and a
broad area suitable for practical application.
U.S. Pat. No. 4,132,824 from which the above-cited U.S. Pat. No.
4,192,842 was divided out claims only an ultrathin membrane
comprising a blend of a methylpentene polymer and an
organopolysiloxane-polycarbonate copolymer.
U.S. Pat. No. 4,155,793 discloses a process for continuously
producing a composite laminar membrane consisting of a web and two
thin polymeric films held thereon in the superimposed state, which
comprises feeding solvent solutions of polymer into two wells
provided in opposing directions on the surface of an aqueous medium
to spread the solvent solutions on the surface of the aqueous
medium, and continuously feeding a web coming into the aqueous
medium at a position intermediate between the two wells thereby to
hold on the web two thin films formed from the solvent solutions
spread on the water surface. This process is characteristic in that
two thin films are continuously formed on a stationary aqueous
medium, and these two films are simultaneously held on one web and
continuously recovered from the surface of the stationary aqueous
medium.
The ultrathin film produced by such a process is used generally for
producing an oxygen-enriched gaseous mixture from air, as is
disclosed in the specification of the above-cited U.S. Patent. Such
a use is embodied as a device for obtaining an oxygen-enriched gas
from air in the specifications of U.S. Pat. Nos. 3,976,451 and
4,174,955.
It is an object of this invention therefore to provide a process
for producing from a hydrocarbon addition polymer a very thin
membrane having a uniform thickness and a substantially equivalent
gas separation factor to the inherent gas separation factor of the
addition polymer.
Another object of this invention is to provide a process which
comprises dissolving a hydrocarbon addition polymer in an organic
solvent which has a suitable surface tension with respect to water
to form a solvent solution of the polymer which has a suitable
surface tension with respect to water, whereby a very thin solid
membrane having a uniform thickness and the desired gas separation
factor is formed on the surface of water.
Still another object of this invention is to provide an ultrathin
solid membrane having a uniform thickness, the desired gas
separation factor and a large area.
Yet another object of this invention is to provide a process for
continuously producing an ultrathin solid membrane having the above
properties by carrying it on a porous sheet-like material.
A further object of this invention is to provide use of an
ultrathin solid membrane having the above properties for the
production of a gas containing a specified component gas (e.g.,
oxygen gas) concentrated from a gaseous mixture (e.g., air) of two
or more gases.
An additional object of this invention is to provide a module used
to concentrate a certain gas by using a solid membrane having the
aforesaid properties, and an oxygen enricher comprising the
aforesaid module for producing an oxygen-enriched gas from the
air.
Other objects and advantages of this invention are apparent from
the following description.
SUMMARY OF THE INVENTION
According to one basic concept of this invention, these objects and
advantages are achieved by a process for producing an ultrathin
solid membrane, which comprises dissolving an addition polymer
derived from at least one monomer selected from the group
consisting of ethylenically unsaturated hydrocarbon monomers and
conjugated unsaturated hydrocarbon monomers in a solvent composed
mainly of a volatile, substantially water-immiscible organic liquid
medium capable of dissolving the addition polymer, said solvent
containing, if desired, another organic compound having a
distribution coefficient k, which is the ratio of the concentration
of the other organic compound in the organic liquid medium to that
in water, of from 0.5 to 35, and said solvent meeting the following
equation
wherein c.sub.1 is the surface tension (dynes/cm) of water, a.sub.1
is the surface tension (dynes/cm) of the solution of the addition
polymer in the solvent, and b.sub.1 is the interfacial tension
(dynes/cm) between the solvent solution and water, and thereafter
allowing the solvent solution of the addition polymer to spread
spontaneously on the surface of a liquid support consisting
substantially of water whereby the solvent in the solvent solution
is removed to an amount sufficient to form a solid membrane on the
liquid surface.
The procedure of the process of this invention involves dissolving
a hydrocarbon addition polymer in a solvent composed mainly of a
substantially water-immiscible organic liquid medium, and allowing
the resulting solvent solution to spread spontaneously on the
surface of a liquid support consisting substantially of water.
DETAILED DESCRIPTION OF INVENTION
Thus, one feature of the present invention is that a volatile
organic liquid medium capable of dissolving the hydrocarbon
addition polymer is used as the substantially water-immisicible
organic liquid medium, and a solvent consisting mainly of the
aforesaid organic liquid medium has liquid surface characteristics
meeting the following equation,
preferably
wherein all symbols are as defined above.
By using a medium having such liquid surface properties, the
resulting solvent solution spreads spontaneously, uniformly and
rapidly on the surface of a liquid support consisting substantially
of water.
Investigations of the present inventors have shown that a mixture
of a certain kind of medium as described above and another organic
compound having a distribution coefficient (k) of from 0.5 to 35,
preferably from 1.0 to 25, is preferred as the solvent composed
mainly of such a medium. The distribution coefficient (k) is the
ratio of the concentration of the other organic compound in the
organic liquid medium to that in water.
The hydrocarbon addition polymer used in this invention is obtained
from at least one monomer selected from hydrocarbon monomers having
an ethylenically unsaturated bond and hydrocarbon monomers having a
conjugated unsaturated bond.
Preferably, it is an aliphatic or cycloaliphatic compound having 2
to 20 carbon atoms, especially 4 to 10 carbon atoms. Examples of
the hydrocarbon monomer are ethylenically unsaturated hydrocarbon
monomers such as ethylene, propylene, butene, isobutene, pentene,
methylpentene, hexene, methylhexene, heptene, cyclohexylpentene,
styrene, .alpha.-methylstyrene, and mixtures of these; and
conjugated unsaturated hydrocarbon monomers such as butadiene,
isoprene, cyclooctadiene and mixtures of these.
Processes for producing addition polymers from these monomers are
known to those skilled in the art.
The addition polymer used in the process of this invention may be a
homopolymer or copolymer of such a monomer. The copolymer may be a
random, graft or block copolymer. The homopolymer is preferred.
Examples of the homopolymer include polyethylene, polypropylene,
polybutene, polyisobutene, polypentene, polymethylpentene,
polyhexene, polymethylhexene, polyheptene, polycyclohexylpentene,
polystyrene, poly(.alpha.-methylstyrene), poly(1,4-butadiene),
poly(1,2-butadiene), polyisoprene, and polycyclooctadiene.
These addition polymers may be used singly or as a mixture of two
or more.
Among these, polybutene, polypentene, polymethylpentene,
polyhexene, polymethylhexene, polybutadiene and polyisoprene are
preferred, and polymethylpentene is especially preferred. These
preferred polymers have a relatively high gas permeability and
pressure resistance and do not soften at room temperature.
In the process of this invention, a solution of such an addition
polymer in the solvent described above is used. The suitable
concentration of the polymer in the solvent solution is about 0.5
to about 15% by weight, preferably about 1 to about 10% by
weight.
Such a dilute solvent solution permits a broader range of selection
of water-immiscible organic liquid media which meet equation (1-a)
and are usable in this invention, and spreads on the surface of a
liquid support consisting substantially of water spontaneously,
uniformly and rapidly. The low concentration of the solvent
solution does not constitute an obstacle when the medium is removed
almost completely by volatilization on the liquid surface to form a
very thin solid membrane on the liquid surface.
In the process of this invention, a hydrocarbon or a halogenated
hydrocarbon may be used as the water-immiscible organic liquid
medium capable of forming the solvent used in providing such a
solvent solution. The hydrocarbon or halogenated hydrocarbon are
preferably alicyclic or aromatic. Examples include cyclohexene,
cyclohexane, trichloroethylene, tetrachloroethylene,
trichloroethane, trichloropropane and mixtures of these.
These water-immiscible organic liquid media are volatile and can
dissolve the aforesaid hydrocarbon addition polymers, but when used
alone, they do not have the liquid surface properties defined by
equation (1-a).
Solvents which meet equation (1-a) are provided by mixing such a
water-immiscible organic liquid medium with another organic
compound having a distribution coefficient, k, of 0.5 to 35,
preferably 1.0 to 25. Solvents of this type are preferred in the
process of this invention.
Examples of the other organic compound are alicyclic or aromatic
alcohols, ketones, amines, aldehydes, carboxylic acids, peroxides
and mixtures of these. For example, cyclohexenol, cyclohexanol,
phenol, cyclohexenone, cyclohexylamine, aniline, furfural, benzoic
acid, cyclohexenyl hydroxy peroxide, and mixtures of these are
especially preferred.
The amount of the other organic compound is about 0.1 to about 15%
by weight, preferably about 0.5 to about 10% by weight, based on
the solvent.
The presence of the other organic compound in the solvent serves to
convert a water-immiscible organic liquid medium, which despite its
volatility and ability to dissolve the addition polymer used in
this invention, cannot by itself be used in the process of this
invention for producing an ultrathin solid membrane having a
uniform thickness, a large area, and a substantially equivalent gas
separation factor to the inherent gas separation factor of the
addition polymer, into a solvent suitably used in the process of
this invention.
It is believed that the other organic compound is mostly removed by
being dissolved in the liquid support consisting substantially of
water from the solvent solution of the addition polymer in the
water-immiscible organic liquid. Since most of the water-immiscible
organic liquid medium in the solvent solution is removed by
volatilization on the liquid support, the process of this invention
may be expressed phenomenally as a process for producing a very
thin solid membrane on a liquid support by using a compound soluble
in the liquid support and a water-immiscible organic liquid medium
which volatilizes into the ambient atmosphere.
The ultrathin solid membrane obtained by the process of this
invention, therefore, is composed of the addition polymer not
containing the other organic compound in a substantially
appreciable amount without subjecting it to any special treatment
after it has been separated from the liquid support.
The process of this invention is carried out by feeding the solvent
solution of the addition polymer gently onto a liquid support
consisting substantially of water. The solvent solution, as already
described hereinabove, spontaneously spreads on the surface of the
liquid support. Accordingly, no special operation is required for
spreading the solvent solution. The solvent solution releases the
solvent therefrom while spreading, and gradually solidifies on the
surface of the liquid support. Releasing of the solvent, namely the
removal of the solvent from the solvent solution, does not require
any special operation, as already stated hereinabove.
The surface of the liquid support should not be vibrated, or the
thin film should not be rippled at least before it is solidified on
the liquid surface.
The solvent solution is fed to the liquid support from a feed means
which is in contact with the surface of the liquid support or is
provided in its neighborhood. Desirably, the feeding is effected in
the direction of gravity. When the solvent solution is to be fed
from a feed means provided in the vicinity of the liquid surface,
the feed means may be situated above or below the liquid surface.
The feed means may be a feed opening. When it is located on the
liquid surface, it may be a slender linear material. In this case,
the solvent solution is fed along the slender linear material. The
suitable length of the linear material is less than about 10 cm,
preferably less than about 5 cm. The feed means may be positioned
up to about 3 mm, preferably up to about 2 mm, above the liquid
surface, or up to about 2 mm, preferably up to about 1 mm below the
liquid surface.
When the feed means is a feed opening, it may be of any shape if it
is adapted to feed the solvent solution continuously or
intermittently at such a rate that the solvent solution fed onto
the liquid surface spontaneously spreads and forms a solid membrane
having a uniform thickness. Since the solvent solution is usually
fed as a dilute solution of the addition polymer, the feed opening
preferably does not have so large an area. Usually, a slit of
narrow width, a slender linear material, or a feed opening of a
small area having any desired shape such as a circle or polygon is
usually employed. The slit having a narrow width preferably has an
opening width of about 0.001 to about 1 mm. The circular or
polygonal feed opening with a small area preferably has an opening
area of about 0.01 to about 3 mm.sup.2, preferably 0.05 to about 2
mm.sup.2.
Preferably, the feed means is a circular or polygonal (e.g.,
triangular, hexagonal, etc.) opening with a small area. Such a feed
means may be the tip of a slender hollow tube, and the tip may be
sharpened.
The solvent solution fed to the liquid support spreads rapidly and
spontaneously on the liquid surface, and simultaneously with, or
subsequently to, the spreading, gradually releases the solvent and
finally solidifies, as stated hereinabove.
The temperature of the solvent solution at the time of feeding is a
factor which affects surface tension and interfacial tension, but
is not so important from the standpoint of controlling these
tensions because it is believed that the temperature of the solvent
solution fed to the liquid support rapidly approaches the
temperature of the liquid support. Rather, the temperature of the
solvent solution at the time of feeding is significant as a
temperature which gives the solvent solution. From this standpoint,
therefore, the temperature of the solvent solution may be about 10
to about 100.degree. C., preferably about 20.degree. to about
70.degree. C.
As stated above, the temperature of the solvent solution fed to the
liquid support is believed to approach the temperature of the
liquid support rapidly. Accordingly, the temperature of the liquid
support affects the surface tensions of the solvent solution and
the liquid support and the interfacial tension between them and
also greatly affects the speed or degree of spontaneous spreading
of the solvent solution on the liquid support. Thus, when the
temperature of the liquid support is too high, volatilization of
the solvent from the solvent solution increases too much, and the
desired speed and degree of spreading are difficult to obtain. On
the other hand, when the temperature of the liquid support is too
low, the volatilization of the solvent is too slow, and the speed
of solidification is decreased.
In the process of this invention, the temperature of the liquid
support is generally about 0.degree. to about 80.degree. C.,
preferably about 1.degree. C. to about 50.degree. C., more
preferably about 3.degree. C. to about 30.degree. C.
For example, when in accordance with the process of this invention,
one drop of a solution of 5 parts by weight of poly-4-methylpentene
in 100 parts by weight of a cyclohexene solvent containing 4.75% by
weight of cyclohexenyl hydroxyperoxide is fed onto a liquid support
composed of water through from a feed opening having an opening
area of about 0.3 mm.sup.2, the solvent solution spontaneously
spreads on the liquid surface immediately upon feeding, and
solidifies in several seconds, for example 1 to 2 seconds, to form
a solid membrane.
The process of this invention can be performed either batchwise or
continuously. By the batchwise operation, a solidified membrane is
formed intermittently on the surface of the liquid support, and by
the continuous operation, a solid membrane is continuously formed
on the surface of the liquid support.
The batchwise operation is carried out, for example, by feeding the
solvent solution in drops to the liquid support, and the continuous
operation is carried out, for example, by continuously feeding the
solvent solution onto the liquid support.
According to the continuous process, a solid membrane having a
broad area can be easily produced. Since the solid membrane formed
on the liquid support by the process of this invention has a very
small thickness, its self-supporting property is low. Accordingly,
the solid membrane formed on the liquid support is usually
separated from the liquid support by supporting it on another
supporting carrier.
According to this invention, the process by the continuous
operation is carried out by continuously feeding a solvent solution
of an addition polymer onto the surface of a liquid support
consisting substantially of water from a feed means so that the
solvent solution does not depart from the liquid surface of the
liquid support to allow the solvent solution to spread
spontaneously on the liquid surface thereby continuously removing
the solvent in the solvent solution to an amount sufficient to form
a solid membrane, and thereafter continuously withdrawing the
ultrathin solid membrane above the liquid surface while carrying it
on a porous sheet-like material.
Since the solvent having the aforesaid liquid surface property is
used, the solvent solution used in the process of this invention
has very good spreadability on the liquid support, and therefore
provides a solid membrane having a broad area, a very small
thickness and a substantially equivalent gas separation factor to
the inherent gas separation factor of the addition polymer.
The solvent solution of the process of this invention having such
good spreadability is firstly very desirable for continuously
producing a solid membrane of a large width using a feed means,
preferably a circular or polygonal feed opening having a small
opening area.
A second feature of the process of this invention by the continuous
operation is that the solvent solution is fed from the feed means
so that it does not depart from the surface of the liquid support.
When the solvent solution is fed at a site away from the liquid
surface, for example in drops, to the liquid surface, the resulting
solid membrane has a striped pattern of non-uniform thickness
attributed to the individual drops of the solvent solution, and
therefore, it is difficult to obtain a solid membrane having a
uniform thickness and the desired separation factor.
In order to perform such desirable feeding of the solvent solution,
it is necessary to provide the feed means in contact with, or in
proximity, to the liquid surface of the liquid support.
The rate of feeding the solvent solution varies depending upon the
type of the feed means, the volatilizability of the solvent, etc.
But when it is to be fed through a preferred feed opening having a
small operning area and being circular or polygonal, it is for
example, about 0.1 to about 20 cc/min, preferably about 0.3 to
about 10 cc/min.
The liquid support may be stationary, or if its surface maintains a
smooth plane, may be flowing. Preferably, the liquid support is
flowing from the feed opening for the solvent solution toward a
site of separating the resulting solid membrane from the liquid
support. By causing the liquid support to flow, the solvent
solution rides on the flow of the liquid support and spreads
spontaneously. Accordingly, continuous variation from the solution
to the solid membrane proceeds very smoothly, and therefore, a
solid membrane having a more uniform thickness and the desired gas
separation factor can be formed.
The solid film membrane formed on the liquid support is separated
and withdrawn from the support surface of the liquid support
continuously while it is carried on a porous sheet-like
material.
The porous sheet-like material usually moves at a fixed speed and
is adapted to get submerged in the liquid support and again come
out onto the liquid surface. The porous sheet-like material can
move such that it separates the solid film from the liquid surface
when it gets submerged in the liquid support or when it comes out
from the liquid support. The speed of movement of the porous
sheet-like material is desirably substantially equal to the speed
of formation of the solid membrane. In other words, care should be
taken so that when the solid membrane is separated from the liquid
surface, a high tension is not exerted on the solid membrane or the
solid membrane does not get loose. Investigations of the present
inventors have shown that this suitable speed can be determined by
taking up the solid membrane forcibly at a nearly constant speed on
the liquid surface of the liquid support in the flowing direction
of the liquid support to form a substantially stabilized flow of
the solid membrane before the solid membrane formed on the liquid
surface is carried on the porous sheet-like material, and then
moving the porous sheet-like material at a speed substantially
coinciding with the speed of the flow of the solid membrane.
The process for producing a solid membrane by the continuous
operation in accordance with this invention is described in more
detail below with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic top plan view of an apparatus suitably used
for the production of a solid membrane by the continuous process of
this invention; and
FIG. 2 is a schematic cross-sectional view taken on line A--A' of
FIG. 1 further showing a porous sheet-like material and other
members required for its motion.
Referring to FIGS. 1 and 2, a smooth liquid surface 14 of a liquid
support 15 is formed in a liquid support tank 10. Usually, the
liquid support 15 can be water. A water supplying pipe 24 provided
in the tank 10 has a plurality of water supply openings 25 for
continuously supplying water to the tank 10. The level of the
liquid surface 14 in the tank 10 is defined by the height of a dam
29. In other words, water overflows beyond the dam 29. In the
drawings, water flows from the water supply openings 25 toward the
dam 29. The water which has overflowed beyond the dam 29 is
discharged out of the tank 10 from a water discharge outlet 32. The
temperature of water is adjusted to a constant point by a
temperature control device (not shown).
A feed opening 21 for a solvent solution of the addition polymer
which is located in contact with the liquid surface 14 exists at
the end of a hollow pipe extending from a reservoir 20 for the
solvent solution. The reservoir 20 includes a heater 22 for heat
insulation or heating which is adapted to maintain the temperature
of the solvent solution at a desired point, and a plunger 23 for
continuously feeding the solvent solution at a constant rate to the
liquid surface 14 from the reservoir 20 through the feed opening
21.
The solvent solution which is continuously fed at a constant rate
to the liquid surface 14 is guided by a guide plate 26 projecting
upwardly beyond the liquid surface 14 and by the flow of water,
spontaneously spreads on the flow of water both in the water
flowing direction and in a direction at right angles thereto. The
guide plate 26 serves to prevent the solvent solution supplied to
the liquid surface 14 from spreading in a direction opposite to the
water flowing direction, and aids in spreading of the solvent
solution in a direction, at right angles to the water flowing
direction. For this purpose, the guide plate 26 is preferably
curved so that its center is located on the side of the feed
opening 21. Especially preferably, the guide plate 26 has a radius
of curvature of about 10 cm to about 1 meter. The feed opening 21
is preferably located on the central line of the arc of the guide
plate 26 at a position about 0.2 cm to about 10 cm away from the
guide plate 26.
The solid membrane 11 formed on the liquid surface 14 is carried by
a porous sheet-like material 12 when the sheet-like material is
submerged in the water. The porous sheet-like material 12 is
supplied from a feed roller 30 and taken up via a rotatable shaft
27 and a guide roller 31. Thus, a solid membrane 13 supported on
the porous sheet-like material 12 is obtained.
In the drawings, the reference numeral 28 represents a wind-up
roller which is used to form a stable constant flow of the solid
membrane on the liquid surface before the solid membrane is carried
on the porous sheet-like material.
Preferably, the feed opening-facing side of the guide plate 26 and
the side wall of the water tank 10 in the solid membrane-forming
zone (i.e., the side wall ranging from the guide plate 26 to the
rotatable shaft 27) are made of a material which does not permit
adhesion of the solid membrane or of a material whose surface is
treated with that material. For example, fluorocarbon resins such
as polytetrafluoroethylene and
copolytrifluoroethylene-hexafluoropropylene are used as the
material which does not permit adhesion of the solid membrane, and
silicone oils such as dimethylpolysiloxane are used as a
surface-treating material having the same property.
According to the process of this invention operated by the
continuous procedure, an endless solid membrane having a width of
as large as about 70 cm can be easily produced, and under optimum
conditions, a solid membrane with a width of about 1 m may be
produced.
The solid membrane provided by this invention is extremely thin,
and has a uniform thickness and excellent gas separating ability.
In particular, the solid membrane produced continuously by the
process of this invention and supported on the porous sheet-like
material has a broad area in addition to having the aforesaid
properties. Accordingly, it can be used for the production of a gas
containing a specified component gas such as oxygen concentrated
therein from a mixture of at least two gases, such as air.
The porous sheet-like material makes up for the weak
self-supporting ability of the solid membrane of this invention,
and scarcely affects the gas separation ability of the solid
membrane of this invention.
The porous sheet-like material may be any of sheet-like materials
having a number of small pores, smoothness and self-supporting
property, such as Japanese paper, nonwoven cloths, synthetic
paper-like sheets, filter papers, cloths, wire nets, filtration
membranes, ultrafiltration membranes, and porous films. Preferred
porous sheet-like materials include porous polyethylene films
(e.g., Celpore, a trademark for a product of Sekisui Chemical Co.,
Ltd.), porous polypropylene films (e.g., Celgard, a trademark for a
product of Celanese Corporation), cellulosic ultrafiltration
membranes (e.g., Fuji-Microfilter, a trademark for a product of
Fuji Film Co., Ltd.), porous polycarbonate films (e.g., Nuclepore,
a trademark for a product of Nomura Microscience Co., Ltd.), and
polysulfone-type ultrafiltration membranes (e.g., Toyo-ultrafilter,
a trademark for a product of Toyo Filter Paper Co., Ltd.). The
porous polypropylene films are especially preferred because of
their good adhesion to the solid membrane of this invention.
If desired, two or more solid membranes of this invention may be
supported as a laminated layer on the porous sheet-like material.
Particularly, an assembly of two solid membranes of this invention
supported in a laminated layer on the porous sheet-like material
(preferably the total thickness of the membranes should be adjusted
to about 50 to about 5000 A) exhibits excellent gas separating
ability when used in separation of gases, and in most cases, shows
a gas separation factor equivalent to the inherent gas separation
factor of the addition polymer forming the solid membrane. It is
rare therefore that more than two solid membranes of this invention
should be laminated in order to obtain the desired gas separating
ability. To superimpose two or more solid membranes of this
invention on the porous sheet-like material, the process of this
invention by the continuous operation is carried out, for example,
in the same way as described above except that a porous sheet-like
material having supported thereon one solid membrane of this
invention is used instead of the porous sheet-like material.
The porous sheet-like material having supported thereon the solid
membrane of this invention (which is sometimes referred to
hereinbelow as a "composite film") can be used as prepared by the
process described above for the separation of gases. Alternatively,
before use in such an application, the composite film may be
heat-treated under temperature and time conditions which do not
cause melting of the solid membrane (for example, in the case of
heating in an atmosphere, heating is carried out at a temperature
of 60.degree. to 300.degree. C., preferably 80.degree. to
200.degree. C., for a period of 3 seconds to 50 hours, preferably 5
seconds to 20 hours) to improve adhesion between the solid membrane
and the porous sheet-like material.
The solid membrane of this invention usually has a thickness of
about 50 to about 3000 A.
The solid membrane is used to obtain a gas having a specified
component gas concentrated therein from a mixture of two or more
gases, as stated hereinabove. For example, it is used in the
production of oxygen-enriched air from atmospheric air, the
production of H.sub.2 -enriched gas from a gaseous mixture
containing H.sub.2 and CO, the removal of H.sub.2 O from a gaseous
mixture containing H.sub.2 O, the removal of SO.sub.2 and/or
nitrogen oxide gases NO.sub.x, from a gaseous mixture containing
SO.sub.2 and/or NO.sub.x and the production of a He-enriched gas
from a gaseous mixture containing He. It is preferably used in the
production of oxygen-enriched air (with an oxygen content of, for
example about 30 to about 45%) from the atmospheric air.
In obtaining a concentrated gas by using the solid membrane of this
invention, it is only necessary to provide a difference between the
partial pressures of a gas to be concentrated on the two surfaces
of the solid membrane. And as the ratio (high pressure/low
pressure) between the partial pressures of the gas increases, there
is obtained a gas in which the gas to be concentrated is more
enriched. For example, in the production of oxygen-enriched air
from the atmospheric air, the pressure of the atmospheric air fed
to one surface of the solid membrane is increased to more than the
atmospheric pressure and the pressure of the other surface is
maintained at atmospheric pressure or reduced pressure. Or the
pressure of the atmospheric air to be supplied to one surface is
maintained at atmospheric pressure and the pressure of the other
surface is reduced.
In order to obtain a gas having a specified gas concentrated
therein from a gaseous mixture of two or more gases, it is
convenient to use a module constructed by using the composite film
in accordance with this invention. The present invention also
provides such a module.
The module of this invention comprises a plurality of basic members
for concentration of gases each of which consists of a solid
support plate and the aforesaid composite film laminated on one or
both surfaces of the solid support plate so that the porous
sheet-like material of the composite film contacts the solid
support plate. It is characterized in that
(1) each of said members has a first gas drawing port for drawing
off a gas having a specified gas concentrated therein, and the
pressure drop in a passage for the concentrated gas in the member
is not more than about 2 mmHg per cm in a direction away from the
first gas drawing port;
(2) the module has a common feed port for feeding a mixture of at
least two gases to the solid membrane surface of each member, a
second drawing port connected to the first gas drawing port of each
of said members, and a third common drawing port for drawing off
the remaining gases formed as a result of concentration by each of
the members; and
(3) in each of the members, the flow of the gaseous mixture is
countercurrent, or angularly displaced, to the flowing direction of
the concentrated gas.
The critical feature of the module of this invention is that it has
the second common gas drawing port connected to the first gas
drawing port of each of the members for drawing the concentrated
gas, and the pressure drop for the concentrated gas in each of the
members is not more than about 2 mmHg per cm in a direction away
from the first gas drawing port. The module of this construction is
compact and light and has excellent separating efficiency.
In the members of this invention, the solid support plate can be
effectively used by placing the solid membrane (composite film) on
its surfaces. This means that the membrane area per member can be
maximized. In other words, if the area of the solid membrane
required for gas permeation is constant, the number of members can
be maximized, and a compact and light-weight module can be
built.
The solid support in the module of this invention has the dual
function of stabilizing the form of the members to support the
solid membrane and of forming a passage for a concentrated gas
which has permeated through the solid membrane. If the gas has
difficulty flowing through the passage, the pressure drop
increases, and therefore, the difference between the pressures
exerted on both surfaces of the solid membrane is small. Hence, the
amount of the gas permeated decreases proportionally to such a
difference in pressure.
It is known that separation of a gaseous mixture becomes better
(the gas separating ability is better) as the ratio of the
pressures exerted on both surfaces of the solid membrane (the ratio
of the pressure on the higher pressure side to the pressure on the
lower pressure side) increases. Accordingly, when the pressure drop
in the passage is high, the pressure on the lower pressure side
increases and the ratio of the pressures decreases. Consequently,
the concentration of the desired gas in the concentrated gas
obtained after permeation through the solid membrane decreases.
For this reason, the solid support plate is suitably of a structure
which minimizes hampering of the passage for the concentrated gas
which has permeated through the solid membrane, namely a structure
which minimizes the pressure drop. A solid support plate in which
the pressure drop is not more than about 2 mmHg, preferably not
more than about 1.5 mmHg, more preferably not more than about 1
mmHg, per cm is preferred.
The pressure drop is measured in this invention in the following
manner.
A sample having a length of 50 cm and a width of 25 cm is cut out
from the member, and the entire surface of the sample is covered
with a gas-barrier film. Both 50 cm-long ends of the sample are
sealed gas-tight. To both 25 cm-long ends is connected a thick
tubular flow opening through which a gas flows without resistance,
for example a tube having a inside diameter of about 8 mm. One end
of the tube is kept open and adapted for decreasing the opening
area, and vacuum suction is effected from the other opening of the
tube. When the flow rate of air is 1 liter/min. on the suction
side, the pressures at both openings are measured, and the
difference between them is defined as the pressure drop. The
measurement is made at 25.degree. C.
The solid support plate in the module of this invention is
preferably a metal plate such as an aluminum plate, a Duralmin
(tradename) plate, a plastic plate such as a polypropylene, hard
vinyl chloride resin, fiber-reinforced polyethylene, terephthalate
or unsaturated polyester plate, or a net-like article such as a
stainless steel net or porous polypropylene plate. When the metal
plate or the plastic plate other than the net-like article is used
as the solid support plate, a spacer is used which forms a
sufficient passage for a concentrated gas between the solid support
and the composite film. The spacer may also be used when the solid
support plate is a net-like article. Various kinds of nets,
nonwoven fabrics, porous materials, etc. are used as the spacer. A
member containing such a spacer can be built by laminating the net,
nonwoven fabric, etc. either alone or in combination on one or both
surfaces of the solid support, and further laminating the composite
film of this invention onto the spacer. It is necessary in this
case to laminate these materials such that the pressure drop in
each member is within the above-specified range.
The spacer has an action of rendering the flow of a gas through the
member easy when the net-like article is not used as the solid
support plate, and its selection is especially important. The net
preferably has coarse meshes and a raised-and-depressed pattern. It
may be made of a plastic or metal, and plastic nets are preferred
from the viewpoint of light weight. The plastic nets preferably
have stiffness, and for this purpose, such materials as
polypropylene, polyethylene terephthalate and polyamides may be
used. Examples of commercially available nets are Vexor of Du Pont,
Netlon of Tokyo Polymer Co., Ltd., and Nip nets of N.B.C.
Industrial Co.
The nonwoven fabrics may be made from polyethylene terephthalate,
polypropylene, polyethylene, polyamides, etc. For example, Unicell
R Type of Teijin Limited, and MF Type of Japan Vilene are
commercially available.
A preferred laminated structure in the member of the module of this
invention consists of a metal plate, a net-like material of both
surfaces of the metal plate, a non-woven fabric on both surfaces of
the net-like material and a composite film laminated to the
surfaces of the nonwoven fabric so that the porous sheet-like
material contacts the non-woven fabric. A member of this structure
shows an especially small pressure drop, has good durability and
prevents deformation of the solid membrane of this invention. In
particular, the use of the non-woven fabric is advantageous in
avoiding rupture of the solid membrane which may occur in the
absence of a nonwoven fabric as a result of deformation of the
solid membrane along the profile of the net-like material
(generally having coarse meshes and an uneven surface). The
nonwoven fabric also has an action of making the flow of a gas
easy. Accordingly, it is preferred that the nonwoven fabric should
have a smooth surface and a smaller mesh opening size than the mesh
opening size of the net-like material.
To make the entire module compact, the thickness of the member
should preferably be as small as possible. It is generally not more
than 5 mm, preferably not more than 4 mm, more preferably not more
than 3 mm.
As stated hereinabove, the member used in this invention has the
composite film on both surfaces of one solid support plate. A first
gas drawing port is provided in this member in order to draw
together the concentrated gas obtained after permeation through the
two composite films. The first drawing port should have a
cross-sectional area and a length which scarcely permit a pressure
drop therein. The member having one drawing port for the two solid
membranes is characterized by the fact that the number of drawing
ports can be reduced to one-half as compared with a member having
two drawing ports for two solid membranes, and the number of
assembling pipes for assembling the concentrated gas from the
drawing ports can be decreased, thus imparting a simple and
convenient structure to the member and the module.
Excepting the drawing port, the entire periphery of the member is
sealed up gas-tight. In other words, it is necessary to provide a
structure which does not permit mixing of a feed gas and the
concentration gas which has permeated through the solid membrane.
To provide such a structure adhesives are preferably used. Examples
of preferred adhesives are epoxy resins, and an ionomer resin
(Sarlin A.RTM.) formed into a film. When an adhesive in a film form
(for instance, Sarlin A.RTM. film) is used, uniform thickness and
good gas-tightness can be achieved.
A plurality of members so produced are built into an array of the
stacked members so as to prevent contact of the solid membranes
with each other and also to provide a passage through which a gas
flows along the outside surface of the solid membrane. The interval
between the members is at least 1 mm, preferably at least 2 mm. A
preferred array for the production of the module of this invention
is the one in which the members at two opposite ends are composed
of a solid support plate and the composite film laminated only to
its one surface so as to avoid exposure of the solid membrane
surfaces.
Spacers of any material are used between the members in building
the array. From the viewpoint of the light weight of the module or
the firmness of the members, the spacers are preferably made of a
rubber or a plastic. It is sufficient that the spacers are located
at the peripheral edges of the members, and are fixed to the member
by, for example, an adhesive.
The array so built is then placed into a box capable of receiving
it to provide the module of this invention. In the array within the
box, the first gas drawing ports from the individual members are
connected to a single assembling pipe. One end portion of the
assembling pipe is drawn from the box to form a second gas drawing
port from which the concentrated gas is drawn off.
The box further includes a common feed port for feeding a gas to be
concentrated from outside the box, and a third common drawing port
for drawing the gas remaining after drawing off the concentrated
gas.
The gas to be concentrated which has been fed into the box from the
common feed port is concentrated through the solid membranes of the
members while it flows through the passages between the member,
thereby giving a concentrated gas (which is drawn out of the box
through the second common drawing port) to the inside of the solid
membrane, and is discharged as the remaining gas out of the box
through the third common drawing port.
The gas to be concentrated which is flowing through the passages
between the members of the array forms a flow which is
countercurrent (for example, as shown in FIG. 4, the gas to be
concentrated is introducd into the passage between the members from
the direction of the first gas drawing port), or is angularly
displaced (i.e., not concurrent), to the flowing direction of the
concentrated gas given to the inside of the solid membrane. By
forming such a flow, the module of this invention has an improved
separating efficiency.
The module of this invention is advantageously used when a gas to
be concentrated is fed at atmospheric pressure from the common feed
port, and the second common drawing port from which the
concentrated gas is drawn off is connected to a pressure reduction
system to reduce the pressure of the passage for the concentrated
gas. Such a module is light in washed and compact.
When, for example, oxygen-enriched air is produced from atmospheric
air, the amount of the air to be fed to the module is usually at
least 5 times, preferably at least 10 times, more preferably at
least 30 times, the amount of oxygen-enriched air drawn from the
module.
An apparatus for actually obtaining oxygen-enriched air from the
atmospheric air using the module of this invention is embodied by
an oxygen enricher provided by this invention.
The oxygen-enriched air (gas) obtained by the oxygen enricher of
this invention can be used therapeutically for patients with
diseases of the respiratory system such as asthma, emphysema and
chronic bronchitis, and for industrial applications in small-size
combustion furnaces and aquaculture. The oxygen enricher of this
invention is characterized by being light in weight and compact,
producing little noise, and being able to produce oxygen-enriched
air having a small temperature difference from the temperature of
the atmospheric air and having a oxygen concentration of not more
than 50%. Accordingly, the oxygen-enriched air obtained from the
oxygen enricher of this invention is especially recommended for use
in medical therapy.
Inhalation of oxygen-enriched air having an oxygen concentration of
more than 60% is known to cause pneumonic ailments or nervous
disorders rather than to perform therapy. It is also known that
oxygen-enriched air having a large temperature difference from the
temperature of the atmospheric air gives an unpleasant feeling to
patients. Evidently, a heavy, bulky and noise-making device is
inappropriate.
The oxygen enricher of this invention has incorporated therein the
module of this invention and further comprises a fan provided in
front of the common feed port of the module, a vacuum pump
connected to the second common drawing port of the module, cooling
and moisture-removing means, an intake-port for the atmospheric
air, an opening for discharging the air, and a housing having these
members provided therein.
Incorporation of the module into the oxygen enricher can be
achieved not only by setting the module of this invention therein,
but also by providing the aforesaid array before the building of
the module of this invention in a preselected area in the oxygen
enricher. The oxygen enricher of this invention includes those in
which the module has been incorporated by any of these methods.
The fan takes the air from the air take-in opening, supplies it to
the module and discharges it from the discharge opening.
The vacuum pump reduces the pressure of the passages for the
oxygen-enriched air in the module and takes out the oxygen-enriched
air out of the oxygen enricher so that concentration is effected
with good efficiency through the solid membranes of this
invention.
In the oxygen enricher, the gas having a reduced oxygen
concentration as a result of going through the module is discharged
from the air discharging opening after it has cooled the vacuum
pump. Before the oxygen-enriched air from the vacuum pump is taken
out of the oxygen enricher, it is cooled with the atmospheric air
taken into the oxygen enricher from the air take-in opening and the
water is removed therefrom. The cooling and water removing means
may, for example, be a hose through which oxygen-enriched air can
flow. The cooled oxygen-enriched air is taken out of the oxygen
enricher without heat exchange with the hot gas to be discharged
which has cooled the vacuum pump.
The fan used in this invention should be capable of supplying the
atmospheric air into the module in an amount at least 5 times,
preferably at least 10 times, more preferably at least 30 times,
the amount of oxygen-enriched air to be drawn off from the module.
A suitable example of the vacuum pump is the one which does not
permit inclusion of fine particles such as oils because the
resulting oxygen-enriched air is used for human inhalation. A
preferred vacuum pump is of oilless type with suppressed noise and
good durability. The ability of the pump varies greatly depending
upon the amount of enriched air, the concentration of oxygen, and
the performance of the separating membrane. For example, when it is
desired to obtain oxygen-enriched air having an oxygen
concentration of at least 35% at 6 liters/min. for therapeutic
purposes, and the ratio of the oxygen permeation coefficient to
nitrogen permeation coefficient of the solid membrane is 3.5, the
pump is required to have such a performance as can secure a flow
rate of 6 liters/min. at an absolute pressure of 270 mmHg. For use
in therapeutic oxygen enrichers, oilless pumps of the diaphragm
type made by Gast Corp. and Thomas Corp. of U.S.A. and Iwai
Kabushiki Kaisha of Japan, for example, are used preferably.
The gas to be discharged from the module can be utilized for the
cooling of the vacuum pump in operation. Preferably, the cooled gas
is discharged out of the oxygen enricher through an air duct having
at least one winding portion in order to prevent leakage of the
pump noises from the oxygen enricher. It is also preferred to apply
a sound absorbing material, etc. to the wall of the housing around
the pump.
A heat exchanger such as a hose is used as the cooling and
water-separating means. In order to cool the oxygen-enriched air
with good efficiency by the atmospheric air to a point near the
temperature of the atmospheric air through the heat exchanger it is
preferred to provide the heat exchanger immediately near the air
take-in opening. Care should be taken so that the surrounding of
the heat exchanger is not warmed by the heat of the vacuum
pump.
From the standpoint of heat conduction, the heat exchanger is
preferably made of a metallic material. A copper material is
especially preferred because it also has an antibacterial effect.
The heat exchanger may be of any of ordinary types. A preferred
type is the one which is compact and permits flowing of water
therethrough. Accordingly, a coil-like heat exchanger is preferred.
The length of the heat exchanger differs depending upon the amount
and temperature of the enriched air. In some case, the length of
the coil is desirably more than 1 meter.
The water-separating means serves to separate the water from the
enriched air. The simplest means is to introduce water-containing
enriched air from a side portion of a cylindrical tube, and
separating the air upwardly and the moisture downwardly. To improve
the separating efficiency, a packing such as a Raschig ring may be
put into the cylindrical tube, and it is also possible to provide
an obstacle such as a shelf therein. The water which gathers in the
lower portion of the water separator is discharged out of it. The
manner of discharging is not particularly restricted. For example,
a receiver tray is provided to pool the water therein. Or the water
is caused to be absorbed by a material capable of well absorbing
water, such as a gauze, and then is evaporated. In the latter case,
water can be evaporated efficiently by using the exhaust gas which
has been used to cool the pump.
If required, the oxygen enricher may also include a column packed
with activated carbon or the like for removing noxious gases such
as NO.sub.x and SO.sub.x and offensive odors from the enriched air,
or a biofilter for removing bacteria from the enriched air. This is
also effective for preventing bacterial contamination in the
conduit portion for enriched air when the oxygen enricher is out of
operation. The oxygen enricher may also include accessory parts
such as alarms for detecting and warning an abnormal condition
during the operation, timers, flow meters, manometers, etc.
The following Examples illustrate the present invention more
specifically. All parts in these examples are by weight.
EXAMPLE 1
Cyclohexenyl hydroxyperoxide (4.75 parts) was dissolved in 90.25
parts of cyclohexene, and 5.0 parts of poly(4-methylpentene-1) (TPX
DX-810, a trademark for a product of Mitsui Petrochemical
Industries, Ltd.) to prepare a solvent solution.
The solvent solution was maintained at 25.degree. C., and one drop
of the solvent solution was dropped onto the surface of stationary
water at 10.degree. C. (liquid support) from an opening having an
area of about 2 mm.sup.2 and spaced about 3 mm above the water
surface.
Immediately then, the droplet of the solvent solution spread on the
water surface to give a substantially circular solid membrane
having its center nearly at the site of dropping. This operation
was repeated a number of times to give circular solid membranes.
The average membrane area of the resulting solid membranes was 567
cm.sup.2.
Two solid membranes so formed on the water surface were supported
on the same surface of a porous polypropylene film from below the
water surface, and were withdrawn from the water (the two solid
membranes were in the superimposed state) to obtain a composite
film.
The composite film had an oxygen permeation velocity of
2.51.times.10.sup.-4 cc (STP)/cm.sup.2 .multidot.sec.multidot.cmHg.
The ratio of the oxygen velocity coefficient to nitrogen permeation
velocity (to be referred to as selectivity) of the composite film
was 3.5.
The surface tension (c.sub.1) of water, the surface tension
(a.sub.1) of the solvent solution and the interfacial tension
(b.sub.1) between the water and the solvent solution, which were
all measured at 25.degree. C., were 72.0, 17.8, and 8.2 dynes/cm,
respectively. The [c.sub.1 -(a.sub.1 +b.sub.1)] value determined
from these measured values (to be referred to as the spreading
factor) was 46.0 dynes/cm.
The distribution coefficient of the cyclohexyl hydroxyperoxide (the
concentration in cyclohexene/the concentration in water) was
2.6.
These results are summarized in Table 1.
It was ascertained that cyclohexenyl hydroperoxide was not present
in the resulting composite film.
The thickness of one membrane was calculated to be 0.08 micron on
an average. (One drop weighed 0.075 g on an average, and the amount
of the polymer in the liquid droplet was 3.75.times.10.sup.-3 g,
and the specific gravity of the polymer was 0.830.)
EXAMPLES 2 AND 8
Example 1 was repeated except that cyclohexylamine, aniline,
.alpha.-naphthol, phenol, benzoic acid, cyclohexanone or furfural
was used instead of cyclohexenyl hydroxyperoxide. The results are
shown in Table 1.
EXAMPLES 9 TO 11
Example 1 was repeated except that poly(4-methylpentene-1) TPX
MX-001, TPX MX-002 or TPX MX-004 (the products of Mitsui
Petrochemical Industries, Ltd.) was used instead of the
poly(4-methylpentene-1) TPX DX-810. The results are shown in Table
1.
EXAMPLE 12
Example 1 was repeated except that a solvent solution obtained by
dissolving 5.0 parts of poly[4-methylpentene-1(70)-decene-1 (30)]
copolymer (charge ratio 70 moles of 4-methylpentene and 30 moles of
decene-1) in a solution of 4.75 parts of cyclohexenone in 90.25
parts of cyclohexene was used instead of the solvent solution used
in Example 1. The results are shown in Table 1.
EXAMPLES 13 TO 15
Example 1 was repeated except that a solvent solution obtained by
dissolving 5.0 parts of poly(1,2-butadiene), poly(1-butene) or
poly(1,4-butadiene) in a solution of 4.75 parts of cyclohexenyl
hydroxyperoxide in 90.25 parts of cyclohexene was used instead of
the solvent solution used in Example 1. The results are shown in
Table 1.
EXAMPLE 16
Example 1 was repeated except that a solvent solution obtained by
dissolving 3 parts of polyisoprene in a solution of 3 parts of
cyclohexanol in 94 parts of cyclohexene was used instead of the
solvent solution used in Example 1. The results are shown in Table
1.
COMPARATIVE EXAMPLE 1
Example 1 was repeated except that a solvent solution consisting of
5.0 parts of poly(4-methylpentene-1) (TPX DX-810) dissolved in 95
parts of cyclohexene was used instead of the solvent solution used
in Example 1. The results are shown in Table 1.
It is seen from Table 1 that in this example, the spreading factor
was only 16.7 dynes/cm. For this reason, spreading of the liquid
droplet on the water surface was poor (average membrane area 202
cm.sup.2), and the resulting solid membrane has numerous pores.
COMPARATIVE EXAMPLES 2 AND 3
Example 1 was repeated except that n-octanol or ethanol was used
instead of the cyclohexyl hydroxyperoxide used in Example 1.
The results are shown in Table 1.
It is seen from Table 1 that in these Comparative Examples, the
spreading factor was within the range of this invention, but the
distribution coefficient between cyclohexene and water fell outside
the range of this invention. The distribution coefficient was 39.1
for n-octanol, but was nearly 0 for ethanol. This is presumably
because the n-octanol has low solubility in water and therefore
remains in the membrane even when the cyclohexene solvent has
evaporated off, and since the n-octanol has no solubilizing power
for poly(4-methylpentene-1), the polymer precipitated and fails to
form a membrane. In the case of ethanol, it is presumed that since
its solubility in water is high, it dissolves in water immediately
after dropping, and it is the same as in the case of using no
additive. The membrane obtained by addition of ethanol is much the
same in appearance as the membrane obtained by using cyclohexene
alone.
TABLE 1 ______________________________________ Other compound in
the solvent Distribution Coefficient (Cyclohexene/ Example Addition
polymer Name water) ______________________________________ 1
Poly(4-methyl- Cyclohexenyl 2.6 pentene-1) hydroxyperoxide (DX-810)
2 Poly(4-methyl- Cyclohexylamine 3.8 pentene-1) (DX-810) 3
Poly(4-methyl- Aniline 2.3 pentene-1) (DX-810) 4 Poly(4-methyl-
.alpha.-Naphthol 10.1 pentene-1) (DX-810) 5 Poly(4-methyl- Phenol
2.3 pentene-1) (DX-810) 6 Poly(4-methyl- Benzoic acid 6.4
pentene-1) (DX-810) 7 Poly(4-methyl- Cyclohexanone 1.6 pentene-1)
(DX-810) 8 Poly(4-methyl- Furfural 0.6 pentene-1) (DX-810) 9
Poly(4-methyl- Cyclohexenyl 2.6 pentene-1) hydroxyperoxide (MX-001)
10 Poly(4-methyl- Cyclohexenyl 2.6 pentene-1) hydroxyperoxide
(MX-002) 11 Poly(4-methyl- Cyclohexenyl 2.6 pentene-1)
hydroxyperoxide (MX-004) 12 Poly[4-methyl- Cyclohexenone 1.8
pentene(70)- decene-1(30)] copolymer 13 Poly(1,2- Cyclohexenyl 2.6
butadiene) hydroxyperoxide 14 Poly(1-butene) Cyclohexenyl 2.6
hydroxyperoxide 15 Poly(1,4- Cyclohexenyl 2.6 butadiene)
hydroxyperoxide 16 Polyisoprene Cyclohexanol 2.2 Comp.
Poly(4-methyl- None -- Ex. 1 pentene-1) (DX-810) Comp.
Poly(4-methyl- Octanol 39.1 Ex. 2 pentene-1) (DX-810) Comp.
Poly(4-methyl- Ethanol --0 Ex. 3 pentene-1) (DX-810)
______________________________________ Measurement of surface and
interfacial tensions (dyne/cm) Interfacial tension between Surface
tension the solvent Spreading of the solvent solution and factor
Example solution water [c.sub.1 - (a.sub.1 + b.sub.1)]
______________________________________ 1 17.8 8.2 46.0 2 21.8 7.0
43.2 3 18.9 6.5 46.8 4 18.9 13.7 39.4 5 21.9 16.7 33.4 6 22.0 15.2
34.8 7 19.5 18.0 34.5 8 16.0 19.5 36.5 9 18.0 7.6 46.4 10 19.4 8.0
44.6 11 17.5 7.9 46.6 12 24.7 15.2 32.1 13 22.7 3.1 46.2 14 22.5
7.2 42.3 15 22.8 10.8 38.4 16 22.7 11.6 37.7 Comp. 22.7 32.6 16.7
Ex. 1 Comp. 22.2 11.4 38.4 Ex. 2 Comp. 18.5 7.6 45.9 Ex. 3
______________________________________ Properties of the solid
membrane Average membrane Oxygen area permeating velocity
Selectivity Example (cm.sup.2) [cc(STP)/cm.sup.2.sec.cmHg] (O.sub.2
/N.sub.2) ______________________________________ 1 567 2.51 .times.
10.sup.-4 3.5 2 548 2.80 .times. 10.sup.-4 3.3 3 324 3.42 .times.
10.sup.-4 2.8 4 403 3.89 .times. 10.sup.-4 2.8 5 369 3.27 .times.
10.sup.-4 2.9 6 384 3.06 .times. 10.sup.-4 3.0 7 333 2.81 .times.
10.sup.-4 3.2 8 363 4.05 .times. 10.sup.-4 2.7 9 527 2.29 .times.
10.sup.-4 3.7 10 518 2.23 .times. 10.sup.-4 3.7 11 590 2.30 .times.
10.sup.-4 3.5 12 340 4.52 .times. 10.sup.-4 2.3 13 326 2.58 .times.
10.sup.-4 2.5 14 342 4.63 .times. 10.sup.-4 2.7 15 414 3.93 .times.
10.sup.-4 2.5 16 308 2.21 .times. 10.sup.-4 2.3 Comp. 202 Because
of numerous pores, a homo- Ex. 1 geneous membrane could not be
obtained. Comp. 514 The polymer precipitated and failed Ex. 2 to
give a membrane. Comp. 323 Because of numerous pores, a homo- Ex. 3
geneous membrane could not be obtained.
______________________________________
EXAMPLE 17
A solution was prepared by dissolving 1.5 parts of
poly(4-methylpentene-1) (TPX DX-810, a product of Mitsui
Petrochemical Industries, Ltd.) in a solution of 3 parts of
cyclohexenyl hydroxyperoxide in 95.5 parts of
trichloroethylene.
The surface tension (c.sub.1) of water, the surface tension
(a.sub.1) of the solvent solution, and the interfacial tension
(b.sub.1) between the water and the solvent solution, which were
measured at 25.degree. C., were 72.0, 21.0 and 15.4 dynes/cm,
respectively. The [c.sub.1 -(a.sub.1 +b.sub.1)] value calculated
from the measured values was 35.6.
The distribution coefficient of the cyclohexenyl hydroxyperoxide
(the concentration in trichloroethylene/the concentration in water)
was 3.1.
The solvent solution was maintained at 70.degree. C., and one drop
of it was gently added to the water surface at 30.degree. C. The
resulting solid membrane had an average membrane area of 280
cm.sup.2 and a thickness of 0.064 micron.
A laminated assembly of two such solid membranes showed an oxygen
permeation velocity of 2.93.times.10.sup.-4 cc (STP)/cm.sup.2
.multidot.sec.multidot.cmHg, and a selectivity of 3.3.
COMPARATIVE EXAMPLE 4
Example 17 was repeated except that a solvent solution prepared by
dissolving 1.5 parts of poly(4-methylpentene-1) (TPX DX-810) in
98.5 parts of trichloroethylene was used instead of the solvent
solution used in Example 17. The resulting solid membrane had an
average membrane area of 50 cm.sup.2. A laminated assembly of two
such solid films showed an oxygen permeation velocity of
3.9.times.10.sup.-3 cc (STP)/cm.sup.2 .multidot.sec.multidot.cmHg
and a selectivity of 1.1.
The surface tension (a.sub.1) of the solvent solution and the
interfacial tension (b.sub.1) between the water and the solvent
solution were 24.0 and 26.2 dynes/cm, respectively. The [c.sub.1
-(a.sub.1 +b.sub.1)] value calculated from these measured values
was 21.8.
EXAMPLE 18
A solvent solution was prepared by dissolving 5 paerts of
poly(4-methylpentene-1) (TPX DX-810) in a solution of 95 parts of
cyclohexene in 5 parts of cyclohexenone.
The solvent solution was maintained at 40.degree. C., and one drop
of it was added dropwise to the surface of water at 10.degree. C.
as a stationary liquid support from an opening with an area of
about 1 mm.sup.2 located about 3 mm above the water surface. The
average membrane thickness was 450 cm.sup.2, and the thickness of
one membrane was calculated to be 0.060 micron on an average.
A composite film composed of two such solid films supported on a
porous polypropylene film showed an oxygen permeation velocity of
5.5.times.10.sup.-4 cc (STP)/cm.sup.2 .multidot.sec.multidot.cmHg
and a selectivity of 3.3.
EXAMPLES 19 TO 26
Example 18 was repeated except that each of the additives shown in
Table 2 was used instead of cyclohexenone. The area and thickness
of the resulting membrane and the properties of a laminated
assembly of two such solid membranes are shown in Table 2.
TABLE 2 ______________________________________ Mem- brane Oxygen
Mem- thick- permeation Se- Ex- brane ness velocity lec- am- area
(mi- [cc(STP)/ tiv- ple Additive (cm.sup.2) crons)
cm.sup.2.sec.cmHg] ity ______________________________________ 19
Ethyl glycol 390 0.070 4.5 .times. 10.sup.-4 3.1 monophenyl ether
20 Anisyl alcohol 420 0.065 5.0 .times. 10.sup.-4 3.2 21
.beta.-phenethyl 380 0.071 4.2 .times. 10.sup.-4 3.1 alcohol 22
2,6-Xylenol 350 0.077 4.5 .times. 10.sup.-4 3.0 23 Isophorone 390
0.070 4.8 .times. 10.sup.-4 3.0 24 Acetophenone 300 0.090 2.2
.times. 10.sup.-4 3.0 25 Anisaldehyde 360 0.075 4.6 .times.
10.sup.-4 3.1 26 Hydroxy- 380 0.071 4.0 .times. 10.sup.-4 3.2
citronellal ______________________________________
EXAMPLES 27 TO 33
Example 18 was repeated except that cyclohexenol was used instead
of cyclohexanone and each of the addition polymers shown in Table 3
was used instead of poly(4-methylpentene-1).
The average membrane areas and thicknesses of the resulting solid
membranes are shown in Table 3. Table 3 also shows, for purposes of
comparison, the average membrane areas of solid membranes obtained
in the same way as above except that cyclohexene alone was used as
the solvent.
TABLE 3 ______________________________________ Membrane Membrane
area (cm.sup.2) thickness Example Addition polymer (*) (microns)
______________________________________ 27 Poly(hexene-1) 550 (230)
0.051 28 Poly(pentene-1) 530 (220) 0.057 29 Polystyrene 620 (410)
0.048 30 Poly(1,4-butadiene) 480 (140) 0.063 31 Poly(decene-1) 720
(310) 0.042 32 Poly[4-methylpentene-1 580 (240) 0.060 (70)-hexene-1
(30)] copolymer (**) 33 Poly[4-methylpentene-1 610 (210) 0.096
(80)-decene-1 (20)] copolymer (**)
______________________________________ (*) The parenthesized
figures show the membrane areas for comparison. (**) The figures in
the smaller parentheses show the mole ratios of the charged
monomers.
EXAMPLE 34
A solvent solution was prepared from 85 parts of cyclohexene, 5
parts of cyclohexenone, 5 parts of cyclohexenol and 5 parts of
poly(4-methylpentene-1) (DX-810). The solvent solution was
maintained at 45.degree. C., and one drop of it was dropped onto
the surface of water at 10.degree. C. in the same way as in Example
18. In the same way as in Example 18, two solid membranes (average
thickness about 0.055 microns) were supported on a porous
polypropylene film (Celgard, a trademark for a product of Celanese
Corporation), and the resulting composite film was placed on a
glass plate and heat-treated for 4 hours at each of the
temperatures shown in Table 4.
The properties of the composite film are also shown in Table 4.
A weight (1 g) was placed gently on the solid membrane surface of
the heat-treated composite film, and then pulled up. The oxygen
permeation properties of the area on which the weight has been
placed were determined. The results are also shown in Table 4.
TABLE 4 ______________________________________ Permeating
Permeating properties after properties after heat-treatment placing
the weight Oxygen Oxygen Heat- permeating Se- permeating Se-
treatment velocity lec- velocity lec- Run temperature [cc(STP)/cm.
tiv- [cc(STP)/cm. tiv- No. (.degree.C.) sec.cmHg] ity sec.cmHg] ity
______________________________________ 1 None 6.9 .times. 10.sup.-4
3.0 >1 .times. 10.sup.-2 1.0 2 20 6.8 .times. 10.sup.-4 2.9
>1 .times. 10.sup.-2 1.0 3 40 6.0 .times. 10.sup.-4 3.0 >1
.times. 10.sup.-2 1.0 4 60 3.7 .times. 10.sup.-4 3.1 3.9 .times.
10.sup.-4 3.0 5 80 3.1 .times. 10.sup.-4 3.4 3.1 .times. 10.sup.-4
3.4 6 100 2.7 .times. 10.sup.-4 3.4 2.6 .times. 10.sup.-4 3.5 7 120
3.0 .times. 10.sup.-4 3.3 2.8 .times. 10.sup.-4 3.5 .sup. 8(*) None
4.5 .times. 10.sup.-4 3.5 > 1 .times. 10.sup.-2 1.1 .sup. 9(*)
80 2.0 .times. 10.sup.-4 3.9 2.1 .times. 10.sup.-4 3.9
______________________________________ (*)In Runs Nos. 8 and 9, the
addition polymer was 4methylpentene-1 (MX002), and the
heattreatment in Run No. 9 was performed at 80.degree. C for 4
hours.
The results in Table 4 demonstrate that heat-treatment under
suitable conditions gives solid membranes of this invention which
have resistance to rupture.
EXAMPLES 35 TO 37
Example 50 was repeated except that each of the addition polymers
in Table 5 was used, and the heat-treatment was performed at
80.degree. C. for 4 hours. The tesults are shown in Table 5.
TABLE 5 ______________________________________ Permeating
Permeating properties before properties after heat-treatment
heat-treatment Oxygen Oxygen permeating Se- permeating Se- Polymer
velocity lec- velocity lec- (membrane [cc(STP)/cm. tiv-
[cc(STP)/cm. tiv- Example thickness) sec.cmHg] ity sec.cmHg] ity
______________________________________ 35 Poly- 3.6 .times.
10.sup.-5 1.7 2.7 .times. 10.sup.05 1.9 styrene (0.13 micron) 36
Poly(1,4- 7.0 .times. 10.sup.-4 2.6 3.1 .times. 10.sup.-4 3.0
butadiene (0.09 micron) 37 Poly(4- 6.1 .times. 10.sup.-4 3.1 2.9
.times. 10.sup.-4 3.3 methyl- hexene) (0.06 micron)
______________________________________
EXAMPLES 38 TO 44
In each run, a solvent solution was prepared by dissolving 5 parts
(5.26 parts in Examples 41 to 44) of each of the addition polymers
shown in Table 6 in 100 arts of a solvent composed of cyclohexene
and cyclohexenyl hydroxyperoxide. The solvent solution was
maintained at 40.degree. C., and one drop of its was dropped onto
the surface of water at 10.degree. C. in the same way as in Example
1.
Two solid membranes obtained were supported on a porous
polypropylene film in the same way as in Example 1, and the
resulting composite film was then heat-treated at 90.degree. C. for
4 hours. The properties of the composite film are also shown in
Table 6.
TABLE 6 ______________________________________ Content of cyclo-
hexenyl Aver- hydro- age Oxygen peroxide mem- permeating Se- Ex- in
the brane velocity lec- am- solvent area [cc(STP)/ tiv- ple (wt. %)
Polymer (cm.sup.2) cm.sup.2.sec.cmHg] ity
______________________________________ 38 4.7 Poly(4-methyl- 552
1.51 .times. 10.sup.-4 3.28 pentene-1) (DX-810) 39 12.2
Poly(4-methyl- 591 1.68 .times. 10.sup.-4 3.05 pentene-1) (DX-810)
40 3.0 Poly(4-methyl- 450 1.62 .times. 10.sup.-4 3.12 pentene-1)
(DX-810) 41 3.0 Poly(4-methyl- 550 1.21 .times. 10.sup.-4 4.03
pentene-1) (MX-001) 42 3.0 Poly(4-methyl- 548 1.20 .times.
10.sup.-4 4.14 pentene-1) (MX-002) 43 3.0 Poly(4-methyl- 548 1.20
.times. 10.sup.-4 3.97 pentene-1) (MX-004) 44 3.0 Poly(1,2- 470
1.55 .times. 10.sup.-5 2.98 butadiene
______________________________________
EXAMPLES 45 TO 53
(1) 600 Parts of cyclohexene distilled at amtospheric pressure was
oxidized with oxygen or air under the various conditions shown in
Table 7, and a solvent containing cyclohexenyl hydroxyperoxide was
produced. The refractive index, measured by the Abbe's
refractometer, of the resulting solvent is also shown in Table 7.
The solvent of Run No. 5 in Table 7 was obtained by diluting the
solvent of Run No. 3 to 2.5 times its volume with cyclohexene.
TABLE 7 ______________________________________ Refractive Reaction
index of Run Molecular temperature Reaction Stir- the solvent No.
oxygen (.degree.C.) (hours) ring (n.sub..alpha..sup.15)
______________________________________ 1 Oxygen 50 33 Yes 1.4500 2
Oxygen 83 61 Yes 1.4538 3 Oxygen 50 47 Yes 1.4527 4 Air 30 72 No
1.4494 5 -- -- -- -- 1.4500 6 Air 30 72 No 1.4494
______________________________________
(2) Five parts of each of the addition polymers shown in Table 8
was dissolved in 95 parts of the solvent obtained as in (1), and a
solid membrane was prepared in the same way as in Example 38 using
the solvent solution.
The properties of the resulting composite film (having two solid
membranes supported on a porous support; heat-treated at 90.degree.
C. for 4 hours) are also shown in Table 8.
TABLE 8
__________________________________________________________________________
N.sub.2 O.sub.2 Average permeating permeating Solvent membrane
Properties velocity velocity Ex- (Run Addition area of the
[cc(STP)/cm.sup.2. [cc(STP)/cm.sup.2. Selec- ample No.) polymer
(cm.sup.2) membrane sec.cmHg] sec.cmHg] tivity
__________________________________________________________________________
45 1 Poly(4-methyl- 552 tough and 0.46 .times. 10.sup.-4 1.51
.times. 10.sup.-4 3.28 pentene-1) homogeneous (DX-810) 46 2
Poly(4-methyl- 620 cloudy at 0.95 .times. 10.sup.-4 2.10 .times.
10.sup.-4 2.21 pentene-1) the surface (DX-810) 47 3 Poly(4-methyl-
591 relatively 0.55 .times. 10.sup.-4 1.68 .times. 10.sup.-4 3.05
pentene-1) tough and (DX-810) homogeneous 48 4 Poly(4-methyl- 450
tough and 0.52 .times. 10.sup.-4 1.62 .times. 10.sup.-4 3.12
pentene-1) homogeneous (DX-810) 49 5 Poly(4-methyl- 544 tough and
0.44 .times. 10.sup.-4 1.48 .times. 10.sup.-4 3.36 pentene-1)
strong (DX-810) 50 6 Poly(4-methyl- 550 tenacious 0.30 .times.
10.sup.-4 1.21 .times. 10.sup.-4 4.03 pentene-1) and (MX-001)
homogeneous 51 6 Poly(4-methyl- 548 tenacious 0.29 .times.
10.sup.-4 1.20 .times. 10.sup.-4 4.14 pentene-1) and (MX-002)
homogeneous 52 6 Poly(4-methyl- 548 tenacious 0.30 .times.
10.sup.-4 1.20 .times. 10.sup.-4 3.97 pentene-1) and (MX-004)
homogeneous 53 5 Poly(1,2- 470 tenacious 0.52 .times. 10.sup.-5
1.55 .times. 10.sup.-5 2.98 butadiene) and (RB-810) homogeneous
__________________________________________________________________________
EXAMPLE 54
A solvent solution was prepared which consisted of 92 parts of
cyclohexene, 3 parts of cyclohexenyl hydroxyperoxide and 5 parts of
poly(4-methylpentene-1) (DX-810).
A solid membrane of this invention was continuously produced from
the solvent solution by using an apparatus of the type shown in
FIGS. 1 and 2.
The solvent solution was maintained at 25.degree. C. in reservoir
20, and continuously fed at a rate of 61 cc/hr to the water surface
14 from feed port 21 in contact with the water surface. Water 15 in
tank 10 was maintained at 5.degree. C. Water was fed through water
supplying pipe 24, overflowed beyond dam 29, and while discharged
from water discharge port 32.
A porous polypropylene film 12 having a thickness of 25 microns and
a width of 30 cm was fed from feed roller 30 into the water via
rotary shaft 27 at a rate of 2 meters/min., and then withdrawn via
guide roller 31.
Thus, a solid membrane 13 of of the invention supported on the
porous polypropylene film was continuously produced. The average
membrane thickness of the solid membrane was 0.075 micron, and the
composite film had an oxygen permeating velocity of
8.3.times.10.sup.-4 cc (STP)/cm.multidot.sec.multidot.cmHg and a
selectivity of 2.6.
COMPARATIVE EXAMPLES 5 AND 6
Example 54 was repeated except that the position of the feed
opening 21 was raised to a point 10 mm above the water surface
(Comparative Example 5), or it was submerged in the water to a
depth of 10 mm from the water surface (Comparative Example 6).
The results are shown Table 9 together with the data of Example
54.
TABLE 9 ______________________________________ Position Selec- of
the feed tivity Run opening State of membrane formation (n=3)
______________________________________ Compara- 10 mm above Wavy.
The membrane width 1.0 tive water occasionally reached 10 to 1.0
Example 5 surface 20 cm and was not stable 1.3 Com- 10 mm Wavy. The
membrane width 1.0 parative below water occasionally reached about
1.2 Example 6 surface 15 to 20 cm and was not 1.2 stable Example
Contacting A stable membrane having 2.5 54 water a uniform width of
more 2.7 surface than 35-40 cm was formed 2.6
______________________________________
EXAMPLE 55
In order to support two solid membranes on a porous membrane using
the apparatus shown in FIGS. 1 and 2, a loop (length 2 m) of the
porous film (thickness 25 microns, width 30 cm) was set between
guide roller 31 and rotatable shaft 27, and the loop was rotated
between the roller and the shaft. Otherwise, the same conditions as
in Example 54 were used, and a laminated assembly of two solid
films supported on the porous membrane was produced.
An about 1.8 m length was taken from the resulting composite film
excepting the joint portion, and at any 10 sites in the
longitudinal and widthwise directions, a membrane sample having a
size of 10 cm.times.10 cm was cut out, and the oxygen permeating
properties of the cut samples were measured. It was found that the
oxygen permeating velocities of the samples were 1.3 to
1.7.times.10.sup.-4 cc (STP)/cm.sup.2 .multidot.sec.multidot.cmHg
and their selectivities were 3.8 to 4.0, showing little variations.
The selectivity of the composite film was better than in the case
of the batchwise operation in which one drop of the solvent
solution was dropped onto the liquid support.
The membrane thickness was determined to be 0.12 to 0.15 micron by
calculating the weight loss of the solid membrane not carried on
the porous film after wiping it off.
EXAMPLE 56
In the apparatus shown in FIGS. 1 and 2, a heat-treating column
having a length of 1 meter was provided between rotatable shaft 27
and guide roller 31.
Using the resulting apparatus, Example 54 was repeated except that
the temperature of the heat-treating column was set at 165.degree.
C.
The solid membrane supported on the porous film could be wound up
on a drum having a diameter of 10 cm.
EXAMPLES 57 TO 59
Example 55 was repeated except that each of the various addition
polymers shown in Table 10 was used instead of the
poly(4-methylpentene-1) used in Example 55. The results are shown
in Table 10.
TABLE 10 ______________________________________ Example Addition
polymer Selectivity ______________________________________ 57
Poly(4-methylpentene-1)(MX002) 4.1 58 Poly(hexene-1) 3.2 59
Poly(1,4-butadiene) 2.9 ______________________________________
EXAMPLE 60
(1) On both surfaces of an aluminum plate having a size of 250
mm.times.500 mm.times.1 mm (thickness) were laminated a
polypropylene net (thickness 500 microns, mesh opening size 14
mesh) and a polyethylene terephthalate nonwoven fabric (thickness
230 microns, basis weight 180 g/m.sup.2) having nearly the same
size as the aluminum plate, in this order, to form a basic
member.
FIG. 3 of the accompanying drawings show schematic perspective view
illustrating the structure of this member.
A cut 42 having a width of 6 mm and a length of 40 mm was provided
in one 250 mm-long side of the aluminum plate 41. To the cut 42 was
fixed a drawing tube 44 for giving a gas drawing port 43 for
drawing off a concentrated gas.
The drawing pipe 44 was built by providing a cylindrical metallic
tube having a thickness of 0.3 mm, an outside diameter of 3.3 mm
and a length of 75 mm, and collapsing a 50 mm-long portion of the
tube from one end thereof until that portion had a thickness of 1.2
mm (the collapsed portion had a width of 4.5 mm). The collapsed
portion was inserted into the cut 42 of the aluminum plate 41 as
shown in FIG. 3, and an epoxy resin was filled in the space formed
between the aluminum plate and the drawing tube to fix the drawing
tube to the aluminum plate. At this time, the end 45 of the
collapsed portion of the drawing tube 44 was positioned so that it
formed a clearance of more than about 5 mm from the deepest part of
the cut. By employing this construction, a gas concentrated by the
solid membrane is collected by the drawing tube from the end 45
through this clearance, and is drawn off from the drawing port
43.
The net 46, the nonwoven fabric 47 and the solid membrane 48 of
this invention were laminated as shown in FIG. 3 to both surfaces
of the aluminum plate 41 having the drawing tube 44 fixed thereto.
The aluminum plate, the net, the nonwoven fabric and solid membrane
were fixed at their peripheral edge portion by an adhesive applied
in a width of 15 mm so as to prevent air leakage from the
peripheral edge.
The basic member for gas concentration showed a pressure drop of
less than 0.6 mmHg per cm.
The solid membrane used was a composite film composed of two very
thin poly(4-methylpentene-1) membranes (total average thickness
0.15 micron; selectivity =3.8) supported on a porous polypropylene
film (thickness 25 microns, maximum pore diameter 0.2 micron) which
was produced continuously by the process of this invention. In
lamination, the porous sheet side of the composite film was
contacted with the nonwoven fabric.
(2) Fourteen members produced as in (1) above were aligned by using
rubber spacers having a thickness of 3 mm and a width of 10 mm
between the members at both edges of the longer sides so that the
drawing ports 43 were positioned in the same direction. A
separately built member consisting of an aluminum plate and
laminated to one surface thereof, the aforesaid net, nonwoven
fabric and solid membrane (i.e., the other side was an aluminum
surface) was superimposed on each of the outermost members of the
resulting array of the 14 members so that the aluminum plate
surface faced outwardly.
Drawing ports from the individual members of the array were
connected to one assembling tube, and the entire structure was
placed in a box.
FIG. 4 of the accompanying drawings shows a schematic perspective
view of the module of this invention in which the array 51 was
placed in the box 50. In FIG. 4, the reference numeral 52
represents the assembling tube connected to the first drawing ports
44 of the individual members, and the reference numeral 53
represents a second drawing port. The reference numeral 54
represents a common feed port for feeding a gas to be concentrated
to the members, and 55, a third common drawing port for drawing the
remaining gas formed as a results of concentration. The arrow shows
the flow of the gas.
A gas fed from the common feed port in the direction of arrow (a)
passed through the individual members of the array 51, and was
withdrawn as the remaining gas from the third common drawing port
55. In other words, the fed gas was concentrated during passage
through the members, and the concentrated gas was collected by the
assembling tube 52 through the first drawing ports 44, and drawn
off from the second common drawing port 53.
Oxygen-enriched air was produced from the air using the module
constructed as above. The second common drawing port 53 was
connected to a vacuum pump (not shown), and while reducing the
pressure, air was fed from the common feed opening port 54 at a
rate of 0.3 m.sup.3 /min. Oxygen-enriched air having an oxygen
content of 41.7% by volume was obtained at a rate of 7 liters/min.
from the vacuum pump.
COMPARATIVE EXAMPLE 7
Members consisting of the aluminum plate, the polyethylene
terephthalate nonwoven fabric and the composite film having an
ultrathin membrane of poly(4-methylpentene-1) supported on the
porous polypropylene membrane were produced in the same way as in
Example 60 except that the polypropylene net was not used.
The members showed a pressure drop of 9.4 mmHg per cm. A module was
built in the same way as in Example 60 using these members. Air was
separated by using the module. When the module was operated while
maintaining the pressure of the assembling tube 52 at 190 mmHg ab.,
oxygen-enriched air having an oxygen content of 26.7% by volume was
obtained at a rate of 2.9 liters/min.
COMPARATIVE EXAMPLE 8
When in the module of Example 60, air was fed from the third common
drawing port 55 at the same feed rate as in Example 60 and the
remaining air was drawn off from the feed port 54, oxygen-enriched
air having an oxygen content of 41.2% by volume was obtained at a
rate of 7 liters/min. when the pressure in the assembling tube 52
was 160 mmHg.
When the amount of air fed was changed to 70 liters/min.,
oxygen-enriched air having an oxygen content of 40.9% by volume was
obtained by the method of Example 60, and oxygen-enriched air
having an oxygen content of 40.2% by volume was obtained by the
method of the present Comparative Example. Furthermore, when the
amount of air fed was further decreased to 35 liters/min. an oxygen
content of 39.6% by volume was achieved by the method of Example
60, but an oxygen content of only 38.6% by volume was achieved by
the method of this Comparative Example.
EXAMPLE 61
An oxygen enricher was built by incorporating the module shown in
Example 60 (see FIGS. 3 and 4).
FIGS. 5 and 6 are schematic perspective views of the oxygen
enricher of this invention. In these figures, the top and that side
surface which appears in front on the sheet surface of these
drawings are removed. FIG. 6 shows the same oxygen enricher as in
FIG. 5 except that the rear side and the front side in FIG. 5 are
reversed.
In FIGS. 5 and 6, the reference numeral 51 represents an array of a
plurality of laminated members including the solid membranes of
this invention, and 52, an assembling tube connected to the
oxygen-enriched air drawing ports of the individual members. The
reference numeral 60 represents a module section having the array
51 therein with an air feed port 54 and a discharge port 55 for the
remaining gas.
The atmospheric air taken into the oxygen enricher from the air
take-in port 62 by the rotation of fan 61 rose in contact with a
cooler 63 through which the oxygen-enriched air was passed, and
went past the fan 61. Then, it was introduced into the module from
air feed port 54 of the module 60 and passed through the array 51.
Then, it left the module from the exhaust port 55 of the module
(see FIG. 5). Then, it entered a pump chamber 64 to cool a pump 65,
and without heat exchange with oxygen-enriched air, was discharged
out of the oxygen enricher via a discharge path. The discharge path
66 was independent so that it was kept from contact with electrical
instruments (not shown in FIG. 6).
On the other hand, by reducing the pressure of the inside of the
individual members of the array 51 by a vacuum pump 65,
oxygen-enriched air formed within the individual members was
gathered by assembling tube 52, and via the vacuum pump 65, was
cooled by flowing through cooling tube 63. Then, water was
separated from the oxygen-enriched air by water separator 68, and
as desired passed through an activated carbon layer or bacteria
filter. Finally, the oxygen enriched air was taken out of the
oxygen enricher from a drawing port 69.
The reference numerals 70, 71, 72 and 73 respectively represent a
switch button for electric power, a flow meter, a pressure gauge
and a timer.
The oxygen enricher had a width of 330 mm, a length of 380 mm, a
height of 700 mm (the side having the air drawing port 69 was
regarded as the front surface), and a weight of 40 kg. When this
oxygen enricher was operated indoors at 15.0.degree. C.,
oxygen-enriched air having an oxygen concentration of 41.7% was
obtained at a rate of 7 liters/min. The temperature of
oxygen-enriched air at an absolute pressure of 160 mmHg was
15.4.degree. C. which was nearly the same as the temperature of the
room. The noise during the operation was 43 horn at a place 1 meter
away from the oxygen enricher.
For comparison, an oxygen enricher was built by using the module
obtained in Comparative Example 5 which did not contain a
polypropylene net. When this oxygen enricher was operated indoors
at 15.0.degree. C., oxygen enriched air having an oxygen
concentration of 26.7% was obtained at a rate of 2.9
liters/min.
* * * * *